A mismatch between GSTR-1 and GSTR-3B sales can occur even without amendments, due to several common reasons.

A mismatch between GSTR-1 and GSTR-3B sales can occur even without amendments, due to several common reasons:

✅ Possible Reasons:

1. Timing Differences:
   • Invoices reported in GSTR-1 of one month but considered in GSTR-3B of a different month.
2. B2C vs. B2B Classification Errors:
   • Misreporting of B2B invoices as B2C or vice versa, affecting auto-population in GSTR-3B.
3. Wrong Table Entries:
   • Sales reported in Table 3.1(a) (taxable supplies) in 3B may differ from GSTR-1 summary tables (e.g., 4A, 5, 6B, etc.).
4. Zero-Rated Supplies (Exports/SEZ):
   • Declared correctly in GSTR-1 but missed or misclassified in Table 3.1(b) of GSTR-3B.
5. Credit/Debit Notes:
   • Reported in GSTR-1 but not reflected in GSTR-3B or vice versa.
6. Rounding-Off Errors:
   • Small mismatches due to rounding off at invoice level in GSTR-1 vs aggregate in GSTR-3B.
7. Technical/Portal Errors:
   • Occasional technical glitches during filing or data sync issues.

Here’s a GSTR-1 vs. GSTR-3B Sales Reconciliation Format to help you identify the mismatch causes and correct them systematically:

✅ Steps to Use the Format:

1. Export GSTR-1 and GSTR-3B data for the period from the GST portal.
2. Compare each category side by side.
3. Note any classification or timing differences.
4. Check if any invoices were missed in either form.
5. Summarize the total mismatch and document corrective actions (e.g., adjust in the next return, file amendment if allowed).

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